Olefinic thermoplastic elastomer composition

ABSTRACT

An olefinic thermoplastic elastomer composition which is excellent in mechanical properties and is substitutable for vulcanized rubbers is provided, which comprises a mixture comprising (A) 40-95 % by weight of an oil-extended olefinic copolymer rubber comprising 100 parts by weight of an olefinic copolymer rubber having a Mooney viscosity (ML 1+4  100° C.) of 150-350 and 20-150 parts by weight of a mineral oil and (B) 5-60% by weight of an olefinic plastic, said mixture being partially crosslinked by dynamic heat treatment in the presence of an organic peroxide. This composition gives superior molded articles free from bleeding of oil on the surface.

This is a continuation of U.S. patent application Ser. No. 07/216,657,filed on Jul. 7, 1988, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to an olefinic thermoplastic elastomercomposition. More particularly, it relates to an olefinic thermoplasticelastomer composition superior in mechanical properties andsubstitutable for vulcanized rubber.

Thermoplastic elastomers (hereinafter referred to as "TPE") have beendeveloped in their uses in a wide variety of fields such as automobileparts, household appliances and general goods because of theircharacteristics that they need no vulcanization and they are able to beworked by molding machines familiar to thermoplastic resins. Among them,olefinic TPE compositions are disclosed in U.S. Pat. No. 3,806,558 andthe like. However, these compositions are inferior to vulcanized rubbersin flexibility, tensile strength at break, ultimate elongation andcompression set and hence are limited in their uses for substitution forvulcanized rubbers.

In order to improve these properties, various attempts have been made,for example, impartation of flexibility by addition of mineral oils suchas naphthenic ones or peroxide-non-curable hydrocarbon rubbers such aspolyisobutylene and an improvement in compression set by increasingcrosslinking degree with the use of a crosslinking assistant such asdivinylbenzene (e.g., U.S. Pat. No. 4,212,787).

However, an improvement of compression set of these compositions byincreasing crosslinking degree causes reduction in flexibility andtensile strength at break and ultimate elongation in tensile tests andfurthermore, bleeding of a softening agent on the surface of thecompositions. Thus, it has been difficult to produce olefinic TPEcompositions having good balance in properties.

SUMMARY OF THE INVENTION

The object of this invention is to provide an olefinic TPE compositionhaving low hardness i.e., 90 or less in Shore A hardness, and beingexcellent in flexibility and mechanical properties, especially, tensilestrength at break, ultimate elongation and compression set,substitutable for vulcanized rubber and good in blow moldability,extrusion moldability or injection moldability.

As a result of the inventors' intensive research to overcome thedrawbacks in the conventional methods, it has been found that acomposition prepared by partially crosslinking a mixture comprising anoil-extended olefinic copolymer rubber previously containing a specificmineral oil and an olefinic plastic is superior in flexibility andmechanical characteristics. This invention is based on this finding.

DESCRIPTION OF THE INVENTION

That is, this invention relates to an olefinic TPE composition which isobtained by partially crosslinking a mixture of (A) 40-95% by weight ofan oil-extended olefinic copolymer rubber containing 20-150 parts byweight of a mineral oil per 100 parts by weight of an olefinic copolymerrubber having Mooney viscosity (ML₁₊₄ 100° C.) of 150-350 and (B) 5-60%by weight of an olefinic plastic.

This invention will be explained below.

(1) The olefinic copolymer rubbers used for (A) in this invention areamorphous random elastic olefinic copolymers such as ethylene-propylenecopolymer rubbers, ethylene-propylene-non-conjugated diene rubbers,ethylene-butene-non-conjugated diene rubbers and propylene-butadienecopolymer rubbers. Among them, especially preferred isethylene-propylene-non-conjugated diene rubbers (hereinafter referred toas "EPDM"). The non-conjugated dienes, include, for example,dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorborneneand ethylidenenorbornene. Ethylidenenorbornene is especially preferred.

More specific examples are ethylene-propylene-ethylidenenorbornene(hereinafter referred to as "ENB") copolymer rubbers having 10-55% byweight, preferably 20-40% by weight of propylene and 1-30% by weight,preferably 3-20% by weight of ethylidenenorbornene and having 150-350,preferably 170-300 of Mooney viscosity (ML₁₊₄ 100° C.).

When propylene content is less than 10% by weight, flexibility isreduced and when more than 55% by weight, mechanical characteristics aredeteriorated. When ethylidenenorbornene content is less than 1% byweight, mechanical characteristics are deteriorated and when more than30% by weight, injection moldability decreases. When Mooney viscosity(ML₁₊₄ 100° C.) is lower than 150, mechanical characteristics aredegraded and when higher than 350, appearance of molded articles isdamaged.

Use of EPDM having Mooney viscosity (ML₁₊₄ 100° C.) of 150-350 affordsan improvement in mechanical characteristics, great increase in tensilestrength at break and ultimate elongation and an improvement incompression set due to increase in crosslinking efficiency. EPDM may beprepared by known methods.

(2) The mineral oil used in this invention is a high boiling petroleumfraction to be added for an improvement of processability and mechanicalcharacteristics, which includes, for example, paraffinic, naphthenic andaromatic ones. A paraffinic petroleum fraction is preferred. If anaromatic component is increased, dying property is enhanced. This is notdesired, because the use for transparent articles or light colorarticles is limited.

(3) The oil-extended olefinic copolymer rubber (A) should contain 20-150parts by weight, preferably 30-120 parts by weight of a mineral oil per100 parts by weight of olefinic copolymer rubber. When an amount of themineral oil is less than 20 parts by weight, flowability of the olefinicTPE composition decreases and especially extrusion processability andinjection moldability are damaged. On the other hand, when it is morethan 150 parts by weight, plasticity markedly increases, resulting indeterioration of processability and besides, properties of the productare degraded.

Mooney viscosity (ML₁₊₄ 100° C.) of the oil-extended olefinic copolymerrubber (A) should be 30-150, preferably 40-100. When it is lower than30, mechanical characteristics are damaged and when higher than 150,molding becomes difficult.

Admixture of a large amount of a mineral oil with EPDM having Mooneyviscosity of 150-350 provides an olefinic TPE composition whichsatisfies insurance of flexibility, an improvement of processability dueto increase in flowability and an improvement in mechanicalcharacteristics.

Mineral oils are familiar as a flowability-improving agent in anolefinic TPE composition. However, according to the inventors' study, aTPE product is not satisfactory when oil-extended EPDM is not used. Inother words, when oil-extended EPDM is not used, addition of a mineraloil in an amount of as large as 40 parts by weight or more per 100 partsby weight of EPDM causes bleeding of the mineral oil on the surface ofthe TPE composition, resulting in staining and sticking of the products,irrespective of viscosity of EPDM. On the other hand, a TPE product isobtained which is superior in properties such as tensile strength atbreak, ultimate elongation and compression set and has neither bleedingof a mineral oil nor staining or sticking on the surface, when anoil-extended EPDM is used, said EPDM containing 20-150 parts by weightof a mineral oil every 100 parts by weight of EPDM having 150-350 ofMooney viscosity (ML₁₊₄ 100° C.). The reason for no bleeding of amineral oil on the surface in spite of a large amount of a mineral oilis considered that the use of EPDM of high Mooney viscosity brings anincrease of upper limit for a permissible oil extension amount of amineral oil and uniform dispersion of the mineral oil previouslyproperly added in EPDM.

Oil extension of EPDM is effected by known methods, e.g., mechanicalkneading of EPDM and a mineral oil in a roll or a Banbury mixer; oradding a given amount of a mineral oil to EPDM solution, followed bydesolvation, for example, by steam stripping. The latter is preferred.Easy operation is effected by using EPDM solution obtained bypolymerization process.

(4) The olefinic plastic (B) used in this invention is polypropylene ora copolymer of propylene and α-olefin of 2 or more carbon atoms. Theα-olefin having 2 or more carbon atoms includes, for example, ethylene,1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-decene,3-methyl-1-pentene, 4-methyl-1-pentene and 1-octane.

Melt flow rate of these polymers should be 0.1-100 g/10 min., preferably0.5-50 g/10 min. When melt flow rate is smaller than 0.1 g/10 min. orgreater than 100 g/10 min., there occur problems in processability.

When an amount of the olefinic plastic (B) in the olefinic TPEcomposition of this invention is less than 5% by weight, flowabilitydecreases, resulting in inferior appearance of molded articles and whenmore than 60% by weight, flexibility is reduced.

(5) Organic peroxides which perform partial crosslinking of a mixturecomprising the oil-extended olefinic copolymer rubber and the olefinicplastic include, for example, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,1,3-bis(t-butylperoxyisopropyl)benzene,1,1-di(t-butylperoxy;3,5,5-trimethylcyclohexane,2,5-dimethyl-2,5-di(peroxybenzoyl)hexyne-3 and dicumyl peroxide. Amongthem, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is especially preferredin smell and scorching.

Addition amount of the organic peroxide can be selected within the rangeof 0.005-2.0 parts by weight, preferably 0.01-0.6 part by weight per 100parts by weight of the oil-extended olefinic copolymer rubber and theolefinic plastic in total. When less than 0.005 part by weight, effectof crosslinking is small and when more than 2.0 parts by weight, controlof reaction is difficult and further, such amount is economicallydisadvantageous.

(6) In production of the composition of this invention, a crosslinkingassistant may be added at the time of formation of partial crosslinkingwith organic peroxide. Examples of the crosslinking assistant areperoxide-crosslinking promotors such as N,N'-m-phenylenebismaleimide,toluylenebismaleimide, p-quinone dioxime, nitrobenzene,diphenylguanidine and trimethylolpropane and polyfunctional vinylmonomers such as divinylbenzene, ethyene glycol dimethacrylate,polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylateand allyl methacrylate. By addition of such a compound, a uniform andgentle crosslinking reaction and a reaction between the olefiniccopolymer rubber and the olefinic plastic take place, whereby mechanicalcharacteristics are improved.

Addition amounts of the peroxide-crosslinking promotor and thepolyfunctional vinyl monomer can be selected within the range of0.01-4.0 parts by weight per 100 parts by weight of the oil-extendedolefinic copolymer rubber and the olefinic plastic in total. Preferredaddition amount is 0.05-2.0 parts by weight. When less than 0.01 part byweight, effect is difficultly developed and when more than 4 parts byweight, this is economicaliy not preferred.

(7) A specific process for obtaining the present TPE composition bypartial crosslinking of a mixture of the oil-extended olefinic copolymerrubber and the olefinic plastic will be explained below.

Oil-extended copolymer rubber (A), olefinic plastic (B) and an organicperoxide and, if necessary, a crosslinking assistant are mixed at aspecific ratio and the resulting mixture is subjected to dynamic heattreatment, namely, melting and kneading. As a mixing and kneadingapparatus, known kneaders such as a non-open type Banbury mixer, atwin-screw extruder and the like can be used. Kneading may be carriedout at a temperature of 150°-300° C. for 1-30 minutes. If necessary,there may be further added auxiliary materials such as inorganicfillers, antioxidants, weather resisting agents, antistatic agents andcolored pigments.

Preferable method for mixing and kneading the oil-extended olefiniccopolymer rubber (A), olefinic plastic (B) and organic peroxidecomprises sufficiently homogeneously kneading the mixture ofoil-extended olefinic copolymer rubber (A) and olefinic plastic (B), ifnecessary, further with the crosslinking assistant and the auxiliarymaterials at a given ratio at 150°-250° C. by a known non-open kneadersuch as a Banbury mixer, then sufficiently blending the resultingcomposition with an organic peroxide by an enclosed mixer such as atumbler or a super-mixer and then subjecting the resulting blend to adynamic heat treatment at 200°-300° C. by a twin-screw continuousextruder which provides strong kneading force.

The auxiliary materials may be added at any stage during production ofthe present composition or at the time of processing of the compositionor at use of the processed articles.

This invention will be illustrated by the following nonlimitingexamples.

Test methods used in the examples and comparative examples formeasurement of properties are as follows.

(1) Mooney viscosity (ML₁₊₄ 100° C.) (hereinafter referred to as"viscosity"): ASTM D-927-57T.

For EPDM, this was calculated by the following formula. ##EQU1## ML₁ :Viscosity of EPDM ML₂ : Viscosity of oil-extended EPDM

ΔPHR: Oil-extension amount per 100 parts by weight of EPDM

(2) Hardness: ASTM D-2240 (Type A, instantaneous value)

(3) Tensile strength at break: JIS K-6031 (JIS-No. 3 dumb-bell, tensilespeed 200 mm/min)

(4) Ultimate elongation: Same as for tensile strength at break.

(5) Compression set: JIS K-6031 (70° C., 22 Hr, compression rate 25%)

(6) Melt flow rate (MFR): JIS K-7210 (230° C., 2.16 kg

(7) Blow moldability: Blow molding machine CAUTEX-NB3B of The JapanSteel Works, Ltd. was used.

Inner diameter of a mandrel: about 25 mm

Blow ratio: about 2.0, a bellows type mold.

Moldability was evaluated by uniformity of thickness and surface textureof a molded product.

Ranks for evaluation are as follows:

∘: Excellent

Δ: Good

x: Bad

(8) Injection moldability: Injection molding machine FS-75N of NisseiPlastic Industrial Co., Ltd. was used.

Molding temperature: 220° C.,

Mold temperature: 50° C.,

Injection: 10 sec., Cooling: 30 sec.,

Injection pressure: Minimum filling pressure necessary for completelyfilling the composition into a mold +2.5 kg/cm², Shape of a mold: 150mm×90 mm×2 mm pin gate.

Evaluation was based on flow mark and sink mark.

Ranks for the evaluation are as follows:

∘: Excellent

Δ: Appeared on only limited parts.

x: Appeared on the whole surface.

(9) Extrusion moldability: USV 25 mmφ extruder of Union Plastics Co.,Ltd. was used.

A full flight type screw with revolving number of 30 rpm.

T-dies and profile dies were used.

Evaluation was on extrusion surface texture for T-die sheet and onreproducibility of edge portion for profile dies.

Ranks for the evaluation are as follows:

∘: Excellent

Δ: Good

x: Bad

(10) Oil bleeding: An injection molded product was left in an oven at70° C. for 24 hours and oil bleeding on the surface of a molded productwas visually evaluated.

Ranks for the evaluation are as follows:

∘: No bleeding

Δ: A slight bleeding

x: Considerable bleeding

EXAMPLE 1

200 Parts by weight of oil-extended EPDM (viscosity=53) obtained byadding to 5 wt. % solution of EPDM (viscosity=242, propylene=28% byweight, iodine value=12, ENB) in hexane a mineral oil (DIANA PROCESS OILPW-380 of Idemitsu Kosan Co.) in an amount of 100 parts by weight per100 parts by weight of EPDM and then desolvating the mixture by steamstripping and 30 parts by weight of polypropylene (MFR=12 g/10 min) werekneaded at 170°-200° C. for 7 minutes by a Banbury mixer and then apelletized master batch was produced from the kneaded product by anextruder.

Then, 100 parts by weight of this master batch was homogeneously blendedwith 0.3 part by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane(hereinafter referred to as "organic peroxide") for 10 minutes by aHenschel mixer.

The resulting blend was subjected to dynamic heat treatment at 250°C.±10° C. for 70 seconds by a twin-screw extruder which provides strongkneading force. Properties and moldability of the resulting pellets wereevaluated.

A plate of 2 mm thick obtained by injection molding was used formeasurement of hardness, tensile test and compression set.

Results of evaluation are shown in Table 1.

EXAMPLE 2

Example 1 was repeated except that 140 parts by weight of oil-extendedEPDM (viscosity=93) prepared by adding to 4 wt. % solution of EPDM(viscosity=170, propylene=30% by weight, iodine value=14, ENB) in hexanea mineral oil (PW-380) in an amount of 40 parts by weight per 100 partsby weight of EPDM and then desolvating the mixture by steam strippingand 20 parts by weight of polypropylene (MFR=12 g/10 min) were used.

Results of evaluation are shown in Table 1.

EXAMPLE 3

Example 1 was repeated except that 2.5 parts by weight ofN,N'-m-phenylenebismaleimice (hereinafter referred to as "BM") was addedto 230 parts by weight of the oil-extended EPDM and polypropylene intotal at preparation of a master batch and 0.3 part by weight of organicperoxide was added to 100 parts by weight of the master batch. Theresults are shown in Table 1.

EXAMPLE 4

In the same manner as in Example 1, a master batch was prepared from 170parts by weight of oil-extended EPDM (viscosity=85) prepared by addingto 6 wt. % solution of EPDM (viscosity=246, propylene=38% by weight,iodine value=10, ENB) in hexane a mineral oil (PW-380) in an amount of70 parts by weight per 100 parts by weight of EPDM, 25 parts by weightof polypropylene (MFR=12 g/10 min) and 2 parts by weight of BM.

Subsequently, Example 1 was repeated except that 0.3 part by weight oforganic peroxide was added to 100 parts by weight of the master batch.Results of evaluation are shown in Table 1.

EXAMPLE 5

Example 2 was repeated except that 2 parts by weight of BM was added to160 parts by weight of the oil-extended EPDM and polypropylene in totalat preparation of a master batch and 0.3 part by weight of organicperoxide was added to 100 parts by weight of the master batch. Resultsof evaluation are shown in Table 1.

EXAMPLE 6

Example 3 was repeated except that a master batch was prepared atblending ratio of 55 parts by weight of polypropylene (MFR=12 g/10 min)and 3 parts by weight of BM per 200 parts by weight of oil-extendedEPDM. Results of evaluation are shown in Table 1.

EXAMPLE 7

Example 3 was repeated except that a master batch was prepared atblending ratio of 15 parts by weight of polypropylene (MFR=12 g/10 min)and 2.5 parts by weight of BM per 200 parts by weight of oil-extendedEPDM. Results of evaluation are shown in Table 1.

EXAMPLE 8

Example 3 was repeated except that 0.6 part by weight of organicperoxide was used. Results of evaluation are shown in Table 1.

EXAMPLE 9

Example 3 was repeated except that a20 parts by weight of calcinedkaolin (SATINETONE SPECIAL of Engelherd Industries, Ltd.) was added asan inorganic filler at preparation of a master batch and an amount of BMwas changed to 3 parts by weight. Results of evaluation are shown inTable 1.

EXAMPLE 10

Example 9 was repeated except that 35 parts by weight of calcined kaolin(TRANSLINK 37 of Engelherd Industries, Ltd.) was used. Results ofevaluation are shown in Table 1.

EXAMPLE 11

Example 3 was repeated except that an amount of organic peroxide waschanged to 0.08 part by weight. Results of evaluation are shown in Table1.

EXAMPLE 12

Example 3 was repeated except that an amount of BM was changed to 1.2parts by weight and an amount of organic peroxide was changed to 0.04part. Results of evaluation are shown in Table 1.

EXAMPLE 13

Example 3 was repeated except that oil-extended EPDM which wasoil-extended by a roll controlled to 100°-120° C. was used. Results ofevaluation are shown in Table 1.

EXAMPLE 14

Example 5 was repeated except that oil-extended EPDM which wasoil-extended by a roll controlled to 100°-120° C. was used. Evaluationresults are shown in Table 1.

COMPARATIVE EXAMPLE 1

Example 1 was repeated except that, in place of the oil-extended EPDM,EPDM and the mineral oil were separately used at preparation of a masterbatch by a Banbury mixer. Results of evaluation are shown in Table 2.

COMPARATIVE EXAMPLE 2

Example 2 was repeated except that, in place of the oil-extended EPDM,EPDM and the mineral oil were separately used at preparation of a masterbatch by a Banbury mixer. Results of evaluation are shown in Table 2.

COMPARATIVE EXAMPLE 3

Example 2 was repeated except that EPDM (viscosity=85, propylene=50% byweight, iodine value=8, ENB) and the mineral oil were separately used atthe same blending ratio at preparation of a master batch by a Banburymixer. Results of evaluation are shown in Table 2.

COMPARATIVE EXAMPLE 4

Example 2 was repeated except that EPDM (viscosity=36, propylene=20% byweight, iodine value=15, ENB) and the mineral oil were separately usedat the same blending ratio at preparation of a master batch by a Banburymixer. Results of evaluation are shown in Table 2.

COMPARATIVE EXAMPLE 5

Example 5 was repeated except that, in place of the oil-extended EPDM,EPDM and mineral oil were used separately at the preparation of a masterbatch by a Banbury mixer. The results are shown in Table 2.

COMPARATIVE EXAMPLE 6

Example 5 was repeated except that EPDM (viscosity=85, propylene=50% byweight, iodine value=8, ENB) and the mineral oil were separately used atthe same blending ratio at preparation of a master batch by a Banburymixer. Results of evaluation are shown in Table 2.

COMPARATIVE EXAMPLE 7

Example 6 was repeated except that, in place of the oil-extended EPDM,EPDM and mineral oil were used separately at the same blending ratio atthe preparation of a master batch by a Banbury mixer. Results ofevaluation are shown in Table 2.

COMPARATIVE EXAMPLE 8

Example 7 was repeated except that, in place of the oil-extended EPDM,EPDM and mineral oil were used separately at the same blending ratio atthe preparation of a master batch by a Banbury mixer. Results ofevaluation are shown in Table 2.

COMPARATIVE EXAMPLE 9

Example 10 was repeated except that, in place of the oil-extended EPDM,EPDM and mineral oil were used separately at the same blending ratio atthe preparation of a master batch by a Banbury mixer. Results ofevaluation are shown in Table 2.

                                      TABLE 1                                     __________________________________________________________________________                   Examples                                                                      1   2   3   4   5   6   7   8                                  __________________________________________________________________________    Blending composition                                                          (Part by weight)                                                              Composi-                                                                           Oil- EPDM 100 100 100 100 100 100 100 100                                tion extended                                                                           Mineral                                                                            100 40  100  70  40 100 100 100                                of   EPDM oil                                                                 master                                                                             Polypropylene                                                                            30 20   30  25  20  55  15  30                                batch                                                                              Calcined kaolin                                                                         --  --  --  --  --  --  --  --                                      N,N'-m-phenylene-                                                                       --  --     2.5                                                                             2   2   3     2.5                                                                               2.5                                  bismaleimide                                                             Cross-                                                                             Master batch                                                                            100 100 100 100 100 100 100 100                                linking                                                                            2,5-dimethyl-2,5-                                                                          0.6                                                                              0.6                                                                                0.3                                                                               0.3                                                                               0.3                                                                               0.3                                                                               0.3                                                                               0.6                             composi-                                                                           di(t-butylperoxy)                                                        tion hexane                                                                   Properties                                                                    Hardness        58 64   60  63  66  80  43  62                                Tensile                                                                            Tensile strength                                                                         52 53   59  61  63  85  43  63                                test at break (kg/cm.sup.2)                                                        Ultimate  650 700 550 570 600 650 430 550                                     elongation (%)                                                           Compression set (%)                                                                           34 35   29  27  26  35  22  20                                Moldability                                                                   Extrusion                                                                          T die     ∘                                                                     Δ                                                                           ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                           Profile die                                                                             ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     Δ                                                                           ∘                      Blow Tickness of wall                                                                        ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                           Surface texture                                                                         ∘                                                                     Δ                                                                           ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                      Injection                                                                          Flow mark ∘                                                                     Δ                                                                           ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     Δ                                                                           Δ                                 Sink mark ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                      Bleeding of oil                                                                              ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                                                                     ∘                      __________________________________________________________________________                   Examples                                                                      9    10   11    12    13   14                                  __________________________________________________________________________    Blending composition                                                          (Part by weight)                                                              Composi-                                                                           Oil- EPDM 100  100  100   100   100  100                                 tion extended                                                                           Mineral                                                                            100  100  100   100   100   40                                 of   EPDM oil                                                                 master                                                                             Polypropylene                                                                            30   30   30    30    30   20                                 batch                                                                              Calcined kaolin                                                                          20   35  --    --    --   --                                       N,N'-m-phenylene-                                                                        3    3      2.5                                                                                 1.2                                                                                 2.5                                                                              2                                       bismaleimide                                                             Cross-                                                                             Master batch                                                                            100  100  100   100   100  100                                 linking                                                                            2,5-dimethyl-2,5-                                                                          0.3                                                                                0.3                                                                                0.08                                                                                0.04                                                                                 0.3                                                                               0.3                              composi-                                                                           di(t-butylperoxy)                                                        tion hexane                                                                   Properties                                                                    Hardness        57   58   61    60    61   68                                 Tensile                                                                            Tensile strength                                                                         55   55   57    56    45   50                                 test at break (kg/cm.sup.2)                                                        Ultimate  490  490  550   530   400  420                                      elongation (%)                                                           Compression set (%)                                                                           28   29   32    37    33   30                                 Moldability                                                                   Extrusion                                                                          T die     ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       Δ                                                                            Δ                                  Profile die                                                                             ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       ∘                                                                      Δ                             Blow Tickness of wall                                                                        ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       ∘                                                                      ∘                            Surface texture                                                                         ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       ∘                                                                      ∘                       Injection                                                                          Flow mark ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       Δ                                                                            Δ                                  Sink mark ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       ∘                                                                      ∘                       Bleeding of oil                                                                              ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                       Δ                                                                            Δ                             __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________                    Comparative Examples                                                          1     2     3    4    5   6    7     8     9                  __________________________________________________________________________    Blending composition                                                          (Party by weight)                                                             Composi-                                                                            EPDM      100   100   100  100  100 100  100   100   100                tion  Mineral oil                                                                             100   40    40   40   40  40   100   100   100                of    Polypropyelene                                                                           30   20    20   20   20  20    55    15   30                 master                                                                              Calcined kaolin                                                                         --    --    --   --   --  --   --    --    35                 batch N,N'-m-phenylene-                                                                       --    --    --   --    2   2    3       2.5                                                                               3                       bismaleimide                                                            Cross-                                                                              Master batch                                                                            100   100   100  100  100 100  100   100   100                linking                                                                             2,5-dimethyl-2,5-                                                                          0.6                                                                                0.6   0.6                                                                                0.6                                                                                0.3                                                                               0.3                                                                                 0.3                                                                                 0.3                                                                                0.3              composi-                                                                            di(t-butylperoxy)                                                       tion  hexane                                                                  Properties                                                                    Hardness        Preparation                                                                         66    57   62   66  60   Preparation                                                                         Preparation                                                                         57                 Tensile                                                                             Tensile strength                                                                        of master                                                                           42    30   35   45  35   of master                                                                           of                                                                                  34ster             test  at break (kg/cm.sup.2)                                                                  batch was                      batch was                                                                           batch was                      Ultimate  impossible                                                                          320   240  240  310 240  impossible                                                                          impossible                                                                          350                      elongation (%)                                                          Compression set (%)   39    42   38   35  38               38                 Moldability                                                                   Extrusion                                                                           T die           Δ                                                                             Δ                                                                            Δ                                                                            Δ                                                                           ∘    Δ                  Profile die     Δ                                                                             Δ                                                                            ∘                                                                      Δ                                                                           ∘    ∘      Blow  Tickness of wall                                                                              Molding                                                                             Molding                                                                            Molding                                                                            Δ                                                                           Δ          ∘            Surface texture was im-                                                                             was im-                                                                            was im-                                                                            Δ                                                                           Δ          ∘                            possible                                                                            possible                                                                           possible                                     Injection                                                                           Flow mark       Δ                                                                             Δ                                                                            Δ                                                                            Δ                                                                           Δ          Δ                  Sink mark       ∘                                                                       ∘                                                                      ∘                                                                      ∘                                                                     ∘    ∘      Bleeding of oil       Δ                                                                             Δ                                                                            Δ                                                                            Δ                                                                           Δ          x                  __________________________________________________________________________

The tables show that, improvements in tensile strength at break,ultimate elongation and compression set in the region of low hardnessare recognized in examples as compared with in comparative examples.Further, improvements are recognized in processability and bleeding ofoil on the surface of molded articles in the examples.

According to this invention, olefinic TPE compositions are providedwhich are improved in processability and oil bleeding on the surface ofmolded articles in addition to improvements in mechanicalcharacteristics such as tensile strength at break, ultimate elongationand which are able to be substituted for vulcanized rubbers.

Uses of the olefinic TPE composition as substitutes for vulcanizedrubbers are as follows: automobile parts such as weatherstrips,headliners, interior sheets, bumper moles, side moles, air spoilers, airduct hoses and various packings; civil engineering and constructionmaterials such as water stops, joint filler materials and window framesfor construction; sports goods such as grips of golf clubs and tennisrackets; industrial parts such as hose tubes and gaskets; and householdappliances such as hoses and packings.

We claim:
 1. An olefinic thermoplastic elastomer composition consistingessentially of a mixture of(A) 40-95% by weight of an oil-extendedolefinic copolymer rubber, and (B) 5-60% by weight of an olefinicplastic, based on the total weight of said composition, wherein saidoil-extended copolymer rubber (A) consists essentially of 100 parts byweight of an olefinic copolymer rubber having a Mooney viscosity (ML₁₊₄100° C.) of 170-350, and 20-150 parts by weight of a mineral oil, andwherein said composition is at least partially crosslinked.
 2. Acomposition according to claim 1 wherein the olefinic copolymer rubberis an ethylene-propylene-non-conjugated diene rubber.
 3. A compositionaccording to claim 2 wherein the ethylene-propylene-non-conjugated dienerubber is an ethylene-propylene-ethylidenenorbornene copolymer having10-15% by weight of propylene and 1-30% by weight ofethylidenenorbornene.
 4. A composition according to claim 1 wherein theoil-extended olefinic copolymer rubber (A) has Mooney viscosity (ML₁₊₄100° C.) of 30-150.
 5. A composition according to claim 1 wherein theolefinic plastic (B) is polypropylene or propylene-α-olefin copolymer.6. A composition according to claim 1 wherein the mineral oil is aparaffinic mineral oil.
 7. A composition according to claim 1 whereinthe oil-extended olefinic copolymer rubber is obtained by adding amineral oil to a solution of an olefinic copolymer rubber.